Durham E-Theses
Sesleria caerulea (l.) ard. ssp calcarea (celak) hegi scop, in the North East of England an ecological study
Yagoobi, Guiti Seyed
How to cite: Yagoobi, Guiti Seyed (1977) Sesleria caerulea (l.) ard. ssp calcarea (celak) hegi scop, in the North East of England an ecological study, Durham theses, Durham University. Available at Durham E-Theses Online: http://etheses.dur.ac.uk/9067/
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2 CONTENTS
Pages
Acknowledgments ii
List of Figs. & Tables iii-iv
Authorities v
Introduction 1-7
Morphology & Anatomy 7-8
Aims of work 8
Study 1 Lowland Populations Experiments 1-3 8-15
Study 2 Thrislington Plantation Experiment 4 16-22
Study 3 Montane Populations Experiments 5 & 5a 22 - 30
Study 4 Transpiration 31 - 38
General Discussion & Further Experiments 39 - 40
Stomata 41 - 44
Plasticity 44 - 45
Transpiration . 45 - 46
Heavy Metals in Population H 46 - 48
Mechanism of Morphogenetic Change 49 - 53
Final Discussion 54 - 55
References 56 - 57 i
SESLERIA CAERULEA (L.) ARD. SSP CALCAREA (Celak.) Hegi Scop,
in the North East of England. An Ecological Study*
by
GUITI SEYED YAGOOBI
Submitted to Durham University for the Degree of Master of Science
The copyright of this thesis rests with the author.
No quotation from it should be published without his prior written consent and information derived
from it should be acknowledged. Botany Department Durham University June 1977 ii
The contents of this thesis are, apart from any text references to published work, entirely the product of my own research and have not been submitted for the candidature of any other degree or diploma.
0-. S&vA-So-^eW
June, 1977
ACKNOWLEDGMENTS
My thanks are due to Professor D. Boulter for research facilities in the Department of Botany; to Dr. David J. Bellamy for his help and supervision; to Mrs. G. Walker for her help both in the laboratory and in the preparation of the thesis. Finally my thanks are due to my parents for all their encouragement and support. • • • XXX
LIST OF FIGURES, TABLES AND PLATES
Page Fig. 1 Distribution of Sesleria in Britain la
Fig. 2 Habit of Sesleria 6
Fig. 3 Tracing of Photograph acetate peel of 7a Sesleria epidermis
Plate 1 Acetate Peel of Sesleria
Plate 2 Acetate Peel Epidermis of Sesleria (Detail) 8a
Table 1 Expt. 1. Data from Populations A. and B. 10
Table 2 Expt. 2, Data from Expt. 2 12
Table 3 Expt. 2, Changes in Structure of Epidermis 12 Result of t test, change in the number of Stomata
Table 4 Expt. 2, Results of t test, change in 13 number of Short Cells
Table 5 Expt. 3, Comparison of Epidermis formed during drought and rains 1976 14-
Table 6 Expt. 4, Number of Stomata, Results of t test 20
Table 7 Expt. 4, Number of Short Cells, Results 21
Table 8 Expt. 5, Number of Stomata, Results of t test 27
Table 9 Expt. 5, Number of Short Cells Results of 28 t test
Table 10 Expt. 6, Number of Stomata and Short cells 30 formed in greenhouse culture
Pig. 4 TRANSPIROMETER 32
Table 11 Expt. 7, Transpiration Rates 33
Table 12 Expt. 8, Transpiration Rates 35
Fig. 5 Expt. 7, Transpiration Rates for first two days 36
Fig. 6 Expt. 7, Transpiration Rates 37 Four day means throughout experiment
Fig. 7 Leaf Blade of Sesleria 39 iv
Table 13 Summary Number of Stomata vs number of 40 Short Cells
Table 14 Summary Number of Stomata per Unit Area 41
Table 15 Soil Moisture 41
Table 16 Climatic Data 43
Table 17 Heavy Metal in Sesleria Leaf Tissue 47 Montane Populations
Table 18 Stomatal Length and Longitudinal spacing 50
Table 19 Summary of number of Stomata, Length and 51 Longitudinal spacing
Table 20 Expt. 4, Stomatal Length and Longitudinal 52 spacing
Fig. 8 Tracings of Stomata from photographs of Acetate peels populations A. and B. 56-5 7 V
AUTHORITIES
Phytosociological Nomenclature Throughout is based on that
Advocated by
LOHENMEYER W etal.
Contribution a L UNIFICATION OU SYSTEME PHYTOSOCIOLOGIQUE
POUR L'EUROPE MOYENNE ET NORD-OCCIDENTALE. MELHORAMENTO
15, 137-151. All authorities quoted in the syntaxonomic sections will be found in this paper with additions from
SHIMWELL, D. (1968). The Phytosociology of Calcareous
Grasslands in the British Isles. Ph.D. Thesis,
University of Durham
For the naming of plant species the following references have been used
FLOWERING PLANTS DANDY, J.E. (1968)
List of British Vascular Plants, Br. Mus. Nat. Hist Lond,
MOSSES WARBURG, E.F. (1963)
Census Catalogue of British Mosses
(3rd ed). Brit. Bryoc. Soc. Publ. Ipswich
LICHENS JAMES, P.W. (1967)
A new check list of British Lichens
The Lichenologist, Vol. 3, 95-153. -1-
INTRODUCTION
Sesleria caerulea (L) Ard. ssp. calcarea (Celak.) Hegi Scop,
is a member of the tribe Festucae of the family Graminae. It is a gregarious grass which forms an important component of sub arctic and arctic alpine grasslands throughout Europe and
Fennoscandia.
Apart from being found mainly on limestone substrata
it appears to tolerate a wide range of soil types and locations
from calcareous syrozems and protorendzinas to mature rendzinas, cf Bryan (1967); from Coastline situations along the Atlantic seaboard of Europe to the higher pastures and screes of the
Centra 1 Alps, and from wet mountain flushes to dry south facing
slopes in lowland situations.
Its distribution in the North East of England is perhaps unique for here in a quite small area it is found in habitats which span the full range of wet to dry, skeletal to mature soils and lowland to montane sub-arctic alpine situations see Fig. 1.
The range of calcareous grassland in the North East of
England has been intensively studied from the phytosociological
stand point by Shimwell (1968). A synopsis of the phytosocio•
logical units in which Sesleria is a dominant or important member
which have been used in this study is given below.
Class Fjestuco-Broraetea
Order Brometalia_erect^L
Alliance Mesombromion •
Sub-Alliance Seslerio-Mesobromion
Association of Sesleria-Helictotrichon
Association Ses 1 er-Caricetura_pu 1 ici^riae
Association Asperulo^eslerietum
Sub Alliance Eu-Mesobromion BCOTIDH -la-
Fig. 1.
B 682/1
SESLEMA CAERULEA (U)Ard. £2 ) • iflOonwirdi o Before 1930
I
\
•
1 1 i 5
"By permission of the Botanical Society of the British Isles, taken from their Atlas of the British Flora and updated by the Biological Records Centre, Monks Wood Experimental Station, Abbots Ripton, Huntingdon."
.9 9 -2-
Association Helictotricho-Caricet^um f^laccae
Class Violetea_calaml.nariae
Alliance Thlaspe^ion ca laminariae
Association Minuartio-^hlaspeet^um
Class Festuco-Brometea_ Br-JBlanq^ R.T.X._ 1943
A class which contains the dry anthropogenic, base-rich grasslands of Central and Western Europe. The limits of these grasslands are somewhat obscure. In the Mediterranean region they are confined to north facing slopes on mountains (Braun
Blanquet 1951) being replaced in the lowlands by the more xeric grasslands of the class Thero-BrachypodieteaBr-B11947, and on the majority of the mountains by the class ONON^DO-ROSMARINETEA
Br-Bl 1947
In the North and especially in the sub arctic climate such grasslands are replaced by grass heaths of the class
Elyno-sesleriatea Br-Bl-1948. In the East their limit is obscured by intergradation with the grasslands of the steppes of
Poland.
Order-Broraetalia_Erecti Br-B1-1936
This order contains the bulk of the dry calcareous grasslands dominated by coarse grasses such as Bromus erectuSj Brachypodium
pinnatum?Festuca ovina and Helictotrichon pratense
Alliance Mesobromion-erecti Br-Blanq. Moor 1938 emend Oberd 1949
The alliance contains most of the familiar chalk and limestone grasslands of the British Isles and also includes some communities
on stabilised calcareous dune systems. The majority of them must
be considered to be secondary in nature being formed on the steeper
scarp slopes layed bare by early deforestation. -3-
Sub AllianceJEu-Mesobromion Oberd 1957
This sub-alliance was created to include almost all the
lowland BSiesobroraion associations which are free from the de-alpine species (Meusel 1939) such as Sesleria caerulea.
Association He ^ictotricho-Ca rice turn f^laccae
An association which in many ways represents a zone of
communities poor in order and alliance character species found
arov.nd the Northern and Western limits of the Cirsl.o_Brometum.
It forms a definite link with the sub-alliance Seslerio-
Mesobromion.
The outlier communities of County Durham form part of a
succession which proceeds to a low scrub community best
referred to the alliance Salicion_arenar/iae_RJUT^X^ 1952^
Sub-Al^iance_Seslerio Mesobromion Oberd 1957
A group of grasslands which occur in a marked zone across
Northern England and Western Ireland and form a floristic link
between the classes. Festuco-Brometea and Elyno-sesierietum.
Association Seslerio-Helictotrichetura
An association peculiar to the magnesian limestone escarp• ment of Eastern Durham at altidues varying between 60 and 160 m
above sea level. The climate of the escarpment is an extension
of the drier eastern climate of South England^ climate type
VIib^Walter and Leith (1967), although the average minimum winter
temperatures are somewhat cooler, average 25°C.
This is the most thermophilous association in the sub-
alliance and forms an important link between the Eu-^Mesobromion
associations to the South and the damper upland associations -4- of the Sesler^o-Mesobromium to the west, four sub-associations are recognisable in the area.
1. Sub-ass, of Encalypta and Plantago maritima although representing a second stage of colonization of disturbed areas, is typical of the shallowest soils where summer drying will be most prevalent.
2. Sub-ass, of Helictotrichon pubescens is fairly widespread above the escarpment being found in small areas which have been disturbed in the past and are now grazed to varying extents.
3. Sub-ass. Typicum occurs in areas of least disturbance on deeper soils which retain their moisture well throughout the summer.
Sub-Ass. Caricetosum pulicariae is found on damp north and west facing slopes which enjoy a more humid micro-climate. The dampness of the habitat is made clear by the abundance of
Ctenidium molluscum, Acrocladium CUBpidaturn and Fissidens cristatus, and locally Pinguicula vulgaris and Brimulia farlnosa, showing a distinct affinity with the association of the Seslerio-Cari.ceturn pulicariae described from the montane limestones of the Pennines.
Association Sesler^o_Car^cetum_puli.cariae
Montane grasslands found at attitudes between 290 m and
730 m above sea level, on steep south and west facing slopes soils ranging from calcareous syrozems to shallow rendzinas.
1. Sub-ass. Typicum is the most widespread and the driest of grassland series being typically found on steep south facing slopes where drainage after rain is rapid. a. Ditrichum flexicaule-^Rhytidium variant is found on the shallow soils which are the most primitive of the calcareous syrozen series. -5-
b) Ca 1 luna-Erapetrum variant on steep slopes with deeper soils which show an accumulation of raw humus in the surface horizon and are best termed a slightly podzolized red-brown calcareous soil. c) Typical variant developed over the deeper, protorendzina soils, root depth being,up to 15 cm.
2. Sub-asSt Kobresietosum
Is found exclusively on Widdy Bank Fell, being typified by the abundance and often dominance of Kobresia simpliciuscula a plant of calcareous alpine flushes of the order TofleIdieta1ia.
Two fades are represented here; in the dampest Carex lepidocarpa becomes an important member of the flora where the water is almost at the surface during all except the driest periods of the year. Typically the soil shows marked signs of gleying and the effective rooting depth appears to be the top few cms. only.
Class Violetea calarai.narj.ae _R/T^X. 1961
Order Vio 1 e ta 1 ia ca larainariae Br-BJL RTX jL943_
Grassland communities of metaliferous strata and metal mine spoil heaps characterized by the presence of Viola calaminaria Lej. a species as yet unrecognized in Britain.
Of the three alliances recognized by Ernst (1965) only one occurs in Britain and that is thei- -6-
AIlianee Thlaspeion Calaminariae_Ernst_1965 a single
association Minuartio-Thl^aspejet^um has been recognized by
Shimwell (1968) from metal spoil heaps. The soils are very
skeletal and although and there may be some accumulation of
humus no soil profile can be said to exist.
It is thus obvious thatj(1) Sesleria caerulea Ssp. calcarea
hence referred to as Sesleria is found in a whole range of habitat
conditions from rapidly drying shallow soils in thermophilous
lowland situations,, to deep wet soils in cold 'sub-alpine'
situations '-(&) the north east of England presents an ideal
situation for detailed study of its ecology.
Infloresence
Leaves
CtuLm
Rhizome
FIG 2 SESLERIA C&ERULEA -7-
Preliminary work (West 1975) has indicated that Sesleria is very plastic especially in relation to size pf the leaves, and number and distribution of stomata on the adaxial surface of leaves.
His conclusions based on a study of 9 populations, 8 of them in northern England and one in Scotland were as follows
1. The size of plants measured both as total leaf length, length of longest leaf and length of the inflorescence were greater the deeper the soil.
2. Stomata1 frequency is negatively correlated with soil depth at any one altitude.
3. In plants from a similar soil depth, ho relationship was found between plant size and altitude, however stomata1 frequency, length of stomatal pore and depth of stomata1 pore were significantly greater at higher elevations. West stated that the variation is mainly due to the plastic response of the plants to their environment, but evidence of genetic differences were also found.
It was therefore decided to attempt to extend our knowledge of the physiological anatomy of the species across the range of habitat conditions found in the north east of England.
MORPHOLOGY AND ANATOMY
Sesleria is an erect wiry, tufted (Fig. 2) perennial which varies greatly in stature both as regards size of leaves and inflorescence. Clapham et al. (1965) give a size range of 15-40 cms.
The leaf blades are more or less flat although being keeled and supplied with bulliform cells may become folded to produce -7a- FIG. 3.
STOMATAL PORE STOMATAL PIT
ACCESORY CELLS I INTERCOSTAL \ \
2 COSTAL
CORK CEL SILICA CELL? -8-
& boat shape leaf especially near the tip.
The most striking feature of the leaf anatomy Prat (1936)
Peelaby (1898) see Fig. 3 and Plates 1 and 2 is the presence of
sunken stomata arranged along the intercostal regions in rows
of two or more. The stomata are supported in the main by
rectangular ^long-cells' (sensu Metcalfe 1960), which may, where
the stomata are crowded become shorter with concave ends making
them appear distinctly saddle shaped.
The costal (above vein) cell rows are devoid of stomata, 'i »
their place appears to be taken by groups of three short-cells
(sensu Metcalfe 1960). Each group appears to consist of
one central silica cell between two cork cells although
staining reactions are not very conclusive. Aims of the Work
1. To compare the distribution of stomata and short cell groups
on the leaf of Sesleria caerulea from the full range of habitats
in which is found growing in the N.E. of England.
2. To investigate the plasticity of the above anatomical
attributes under cultivation.
3. To investigate the relationship between stomatal number and
transpiration rate in two contrasting field populations.
Study 1 Lowland populations on magnesian limestone
Two populations were studied from the Cassop Vale area of
lowland County Durham both at approximately 160m above sea
level.
Population A is situated on the N.E. facing ledges of a disused
quarry where maximum soil depth does not exceed 2 cms^in a
position where rapid drying out between rains is inevitable. Plate I
1 Hi i ammm
«9 f 0
Plate
•
1 -9-
Table A presents phytosociological data for the closed communities of the ledges
V-Sesleria caerulea 3.3 IV- Carex flacca +.1 III-Helianthemum chamaecystus + .2 V- Plantago maritima 1.2 V-Encalypta vulgaris + .2
(In the table, the roman figures given before the plant names is a measure of constancy of occurrence in 10 sample plots and the arabic figures are the abundance sociability estimates
Braun Blanquet (1956) for the plot from which the samples were taken. This format is used throughout the thesis.
N.B. only the important (characteristic) species are listed.) a The community is best classified with the sub association of Encalypta and Plantago maritima of the Sesleri© Helicto- trichetum
Population B
In contrast is taken from a wide area of deep soil (up to 40 cm). Its aspect is north and the site is supplied by seepage water from a considerable area of magnesian limestone,.
Table B presents phytosociological data from the relevant communities.
Table B
V Sesleria caerulea 3.4 V Carex panicea +.1 IV Carex flacca +.2 III Pinguicula vulgaris +.2 IV Carex pulicaris 1.2 IV Ctenidium molluscum + .2 V Acroccadium cuspidatum 1.2 - 10-
Th e community of the area is best referred to the
Sub. ass. Caricetosum pulicariae
Experiment 1
Collection and laboratory study 20 plants collected at random from the communities were stored in polythene bags at 0°C before the following measurements were made on each. 1. Length of the longest leaf; 2. number of stomata per unit area in the mid section and top section of the longest leaf; 3. number of short cell groups (hence called short cells) per unit area in the mid section and top section of the longest leaf.
Results
The results are summarised in Table 1 in which the significance levels derived from student t tests are shown.
TABLE 1
Significance
Difference Pop B
Length of longest leaf (DUB) 4.9 + 0.4 * * * 13.8 - 1.8 + Number of Stomata/Unit 669 24 * * * 417 ± 18 area Mid section Number of Stomata/Unit 649 + 73 * * * 454 - 31 area Top section Number of Short Cells/Unit 372 + 36 NS 336 ± 25 area Mid section Number of Short Cells/Unit 315 + 25 NS 302 - 25 area Top section
Significance Levels (this notation is used throughout the thesis)
* * * p B 0.001; * * p - 0.01; * p - 0.05; NS - not significant
Conclusions The longest leaves in population A are significantly shorter
than those of population B. The number of stomata per unit leaf ( * All measurements of stomatal and short cell numbers refer to the adaxial leaf surface, throughout the thesis.) -11-
are area/significantly greater in population A than in population B. There is no significant difference between the number of short cells per unit area of leaf of the two populations. Experiment 2
Aim to investigate the "plasticity" of the two populations
Method
50 plants were collected at random from each population. On return to the laboratory they were potted separately in 20 cm. plastic pots filled with John Innes No. 1 compost. The pots were then arranged in two latin squares in the greenhouse, each one a mixture of 25 of each type of plant. One set designated 'wet treatment' were watered every day, the other set designated dry treatment were watered once every 7 days. The length of all leaves of every plant were measured. The experiment was terminated after 6 weeks, when the following measurements were made:
1) Length of all leaves (hence it could be calculated which
leaves had grown the most); 2) length of the longest leaf;
3) the following measurements were then made on a) the five
leaves that had grown the most, and b) five new leaves.
Number of stomata and the number of short cells in the
mid section of the leaf. The results are summarised and
statistical comparison of each data set using the student t
test is shown below -12-
TABLE 2
Stomata Cells + 1. Population A Field raid section 669 24 372 - 36 2. A " top " 649 + 73 315 ± 25 3. B mid " 417 + 17 336 ± 25 4. " B " top » 454 + 30 302 ± 35 5. A Laboratory wet 482 + 50 225 ± 27 grown most 6. A Laboratory wet 495 + 35 234 ± 48 new leaves 7. A Laboratory dry 466 + 35 255 ± 21 grown most 8. A Laboratory dry 503 + 34 258 ± 25 new leaves 9. " B Laboratory wet 403 + 72 375 - 23 grown most 10. " B Laboratory wet 507 + 52 306 ± 34 new leaves 11. " B Laboratory dry 513 + 23 517 ± 53 grown most 12. " B Laboratory dry 548 + 20 401 ± 55 new leaves
TA BLE 3 STOMATA
2 3 4 5 6 7 8 9 10 11 12 1 NS *** *** *** *** *** *** *** *** *** *** 2 NS ** * * * ** * NS 3 NS * NS ** NS ** ** *** 4 NS NS NS * NS * * **
5 NS NS NS NS NS NS NS 6 NS NS NS : NS NS NS 7 NS NS NS NS NS 8 NS NS NS NS 9 NS NS 10 NS NS 11 NS 12 -13-
TABLE 4
SHORT-CELLS
1 2 3 4 5 6 7 8 9 10 11 12 1 NS NS NS ** ** ** ** NS ** NS 2 NS NS ** * ** NS NS NS ** 3 NS * * ** NS NS ** * 4 NS NS NS NS NS ** 5 NS NS NS ** NS ** ** 6 NS NS * NS ** ** 7 NS * NS • • NS 8 * NS ** NS 9 NS ** NS 10 ** **
12 CONCLUSIONS STOMftTA Under the conditions of the experiment new leaf tissue produced by the plants of population A (dry), produce significantly fewer stomata per unit leaf area than in the field situation. In contrast the new leaf tissue produced o by the plants of. the population B (wet), produce significantly
more stomata than when in the field situation.
Short-Cells
Under the conditions of the experiment the new leaf
tissue produced ;by the plants of population A (dry) show a significant decrease in the number of short-cells in the
treatments. In contrast those of population B (wet) show a significant increase in the number of cells when grown in the
dry although there is no significant change in the wet
treatment. -14-
Experiment 3 The summer of 1976 was exceptionally dry for a period of some two months when the drought was terminated by torrential rains. It was decided to attempt to make use of these extreme climatic conditions to test anatomical variability in a field population. To this end the longest new leaves were collected from 20 selected plants at random from the contrasting populations at Cassop in late autumn. Counts were made of the stomata and short- cells in the top section (grown during the drought period) and the basal section (grown during the rainy period).
Although it is felt that direct comparison between years is impossible because of the multitude of environmental
variations, it at least seems safe to compare the number of stomata in the leaf tissue produced during the drought with that produced in the autumn rains.
Statistical analyses of the results are summarised below.
Results
Table 5
Sample (20 of each) Stomata Cells 1) Population A. Top (Drought) 642 ± 39 302 - 23 2) Population A. Bass (Rains) 532 - 15 338 t 15 3) Population B. Top (Drought) 614 - 20 410 ± 17 4) Population B. Base (Rains) 437 - 23 296 - 21 -15-
Table 5 (Con'd)
STOMATA
A top A base B top B base A top *** NS ***
A base * *
B top *** B base
[ORT-CELLS
A top A base B top B base
A top NS *** NS
B top ** B base
Conclusions Stomata During the drought period both populations were producing leaf tissue with a similar number of stomata per unit area. In contrast during the wet period population A is producing more stomata per unit area of leaf tissue than population B, thus reverting to the normal field situation. Short-Cells During the drought period, population B was producing significantly more cells per unit area of leaf tissue than population A. This backs up the findings of experiment 2. -16-
STUDY 2 Thrislington Plantation
Experiment 4
A series of six contrasting populations were selected for study from the lowland area of Thrislington plantation in County Durham, altitude W-w above sea level. Details of the ecology and phytosociology of the chosen populations are given in each section below. Collections were made in late autumn 1976 and measurements of the following were made from each population. Number of stomata and number of short cells, from the top section of each leaf that is of tissue formed during the drought period. To allow further study of the possible effects of the drought measurement were also made to allow comparison between the top and the base of the leaf, the latter being produced during the wet autumn period.
Population C Habitat
Skeletal grassland on the edge of an old trackway.
The soil is a protorendzina^ maximum rooting depth approximately
2 cms.
Phytosociology V Sesleria caerulea 2.2 V Hypochaeris radicata +.1 III Hypericum montanum +.1 V Ceratodon purpureus +.2 IV Encalypta vulgaris 1.2 II Epipactis atrorubens + II Crataegus monogyna + -17-
Syntaxonomy Association Seslerio Helictotrichetum Sub-Ass. Encalypta and Plantago maritima
Results (Sample size 10) Stomata Cells
Drought 837 - 11 351 - 14 Autumn rain 725 - 27 300 - 15
Population D
Short turf grassland found on or near marked breaks of slope. The soils are rendzinas, the maximum rooting depth being 6 cms.
Phytosociology
V Sesleria caerulea 2.3 V Helictotrichon pubescens 1.1 IV Daucus carrota +.1 IV Centaurea nigra 1.1 V Plantago media 1.1
Syntaxonomy
Association Seslerio_Helietotricheturn Sub-Ass. Helictotrichon pubescens
Results
Stomata Cells Top (Drought) 715 - 43 359 - 14
Population E
Restricted tracts of grassland, although on gentle south facing slopes are but little effected by grazing by farm stock.
The soils are best described as rendzinas, maximum rooting depth 30 cm. -18-
Phytosociology
II Sesleria caerulea 1.2 V Helictotrichon pubescens 1.1 V Helictotrich on pratense 1.1 V Poterium sangulsorba +2 IV Carlina vulgaris +2 III Anthyllis vulneraria +.1 II Linum anglicum +2
Syntaxonomy
Sub-Alliance Mesj>brom^n-erecti Association He1ictotricho-Cariceturn-flaccae
Results (Sample size 10)
Stomata Cells Top (Drought conditions 650 - 15 284 - 23
Population F
A single small stand of grassland which is being invaded by a hybrid population of willows. (Salix repens x Salix aigra). it is in reality a damper version of the above being situated close to the base of a main south east facing slope and in part is subject to seepage water draining off the slope.
Phytosociology (NB a single stand)
Sesleria caerulea 1.2 Helictotrichon pubescens 2.3 Carex flacca 1.1 Koeleria cristata 1.1 Primula farinosa +2 Valeriana dioica 1.1
Syntaxonomy Association He lictotricho-Caricetura-flaccae
Border Community with developing scrub related to the
Alliance Salicon arenariae R.T.X. 1952 -19-
Results (Sample Size 10)
Stomata Cells
Top (Drought) 604 - 33 250 - 9
Population G Tracts of grassland on a range of slopes which are subject to little or no-grazing by farm stock. Soils are rendzinas with a maximum depth of 50 cms.
Phytosociology
V Sesleria caerulea 2.3 V Helictotrichon pratense 1.1 II Epipactis atrorubens +2 III Betonica officinalis +1 III Campanula rotundifolia +1 IV Carex flacca
Syntaxonomy
Association Seslerio Mesobromion
Sub-Ass. Typicum
Results (Sample Size 10)
Stomata Cells Top (Drought) 505 - 17 241 ± 70
Base (Wet) 450 - 27 216 - 12
The results are summarised in Table 6, where the results.of comparison using student t test are given. -20-
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•H a d o CQ CQ •H EH 1 SH O ss V CQ W E$ a 09 a rH +1 !25 o r-l EH CQ # 8 in CO -p O £ 09 CQ * «H * O r-l
+1 + 1 s CM o a m o O CO EH P CQ co
0 W a a0 fii a 0a a +> EH EoH EH EoH c> si n ci CJ o Q H o DO -p •H o Q> +J CS 3 0 a a o o W -22-
Conclusions
There is a positive correlation between the stomata and the arbitrary scale of depth/dampness of the soil. The number of stomata decrease significantly with increasing depth/dampness of the soil. The effect of the rain after the drought has been similar to decrease significantly the number of stomata formed on the leaves of both plants of the extreme 'wet* and extreme 'dry' populations.
The correlations and 'effects' on the short cells are not nearly as clear cut. Increasing depth/dampness of the soil goes hand in hand with a decrease in the number of the short cells. The effect of rain compared to drought is to significantly decrease the number of cells in the extreme dry population, and exactly the opposite in the population G from the wet field conditions.
Study 3 Montane populations
Experiment 5
All the following populations are situated at about 540 m OD on the Widdy Bank Fell National Nature Reserve in County Durham.
The following attributes were measured from each:
1) Number of stomata; 2) Number of cellSj per unit area in the top section of the leaves formed in 1975 and during the drought and the basal section formed during the autumnal rains of 1976.
Population H
Habitat details
Skeletal grassland developed on an old spoil heap from the Cow Green lead/barytes mine. No soil as such exists, the plants are rooted in the fines between the spoil. The soils are subject to very rapid drying after rain. -23-
Phytosociology
III Sesleria caerulea +2 IV Thlaspi alpestre +1 IV Anthoxanthum odoratum +1 III Carex capillaris +2 IV Plantago lanceolata +2 III Minuartia verna +2
Syntaxonomy
Association Minuartio Thlaspeeturn
Results (Sample size 10
1975 Stomata Cells 385 - 17 91 t 2
1976 Autumn Top 532 ± 17 395 - 11 Base 521 - 17 362 - 11
Population I
Grassland on soils developed on steep slopes or close to breaks of slope. The soils are at the best considered to be calcareous syrozems providing a maximum rooting depth of 2 to
3 cms.
Phytosociology
V Sesleria caerulea 2.1 V Gallium sterner! + V Cornicularia aculeata 1.1 IV Ditrichum flexicaule +2 IV Hieracium pilose11a 1.1 III Barbula fallax +2 III Helictotrichon pratense 1.1 III Carex ericetorum + IV Carex pulicaris 1.2 -24-
Syntaxonomy
Association Seslerio-Caricetum pulicariae Sub-Ass. Typicura Variant Ditrichum and Rhytidium
Results (Sample size 10) 1975 Stomata Cells Top 677 - 37 194 - 23
Population J
Grassland with a mixture of heath species developed on gentle slopes on slightly podsolised red-brown calcareous soils, rooting depth not more than 10 cms.
Phytosociology V Sesleria caerulea 2.3 IV Gallium sterneri 1.1 IV Cornicularia aculeata 1.2 V Calluna vulgaris +2 III Empetrusa nigrum +2 I II Carex pulicaris 1.2
Syntaxonomy Association SesJ.erio Gajricetum jpulicariae Sub-Ass. Typicum Variant Calluna/Empetrum
Results (Sample size 10) 1975 late Stomata Cells 645 ± 55 279 - 15 1976 Top (Dry) 660 - 2 453 - 14 Base (Wet) 576 - 19 358 - 12 -25-
Population K
Extensive grasslands developed over a range of slopes on undulating ground, the soils are protorendzinas up to 15 cms deep.
Phytosociology
V Sesleria caerulea 3.3 IV Gallium sterneri 1.1 IV Cornicularia aculeata 2.2 III Carex pulicaris 1.2
Syntaxonomy Association Seslerio Cariceturn pulicariae Sub-Ass. Typicum Variant typicum
Results (Sample size 10)
Stomata Cells 1975 614 - 17 277 ± 28 1976 top 643 - 21 361 - 11 base 596 - 20 364 - 12
Population L Habitat details Grasslands developed in damper areas, in some cases depressions in others near the base of main slopes adjacent to flushes. Soil profile deep, to 30 cms.
Phytosociology V Sesleria caerulea 1.2 III Carex pulicaris 2.2 IV Kobresia simpisiuscula 2.3 V Carex flacca 1.2 IV Carex panicea +1 -26-
Syntaxopomy
Sub-Ass. Kobriesietosum
Results (Sample size 10)
1976 Stomata Cells Top 549 - 18 445 - 14 Base 541 - 17 378 - 12
Population M As above but taken in the areas where there is an abundance of Carex lepidocarpa in the community. Rooting depth less than 4 cms.
Results (Sample size 10)
Stomata Cells 1975 796 - 68 88 ± 10
The results as summarised in Table 8 and 9 where the results of comparison using the student t test are shown
Conclusions In the main the same trends are shown as for the lowland populations. The populations situated on the dry skeletal soils have more stomata than those on the deeper wetter soils, the differences are however in many cases not significant.
There are however two marked exceptions. The plants on the thin skeletal soils on heavy metal spoil heaps have significantly fewer stomata, and those on the very wet flush soils appear to have significantly more stomata than they should if the wet to dry series is correct. -2 7-
00 § CD ss +i «
a a +1 •J . K CD s CD rt iz; P (=> in m CM
(4 r» O rH M o CM CD +» + 1 +1 w a to CD -rt CO CO CD O rH 05 Q S CO CO in 00 o T3 (3 cn -p m cn CO m 01 CD * +i a •-3 +i +1 CD t» * * 0) m o CO CD Q Q CO CO rv CJ CO m CO CO CM +> oo •rt a 3 r> rH 0 CO a v ri-Ht M +1 OS a A >> a X! fn c- CO -p CO P c- i 00 o p m CO •» CO CO to o rH >» sa In k -P * * a CD jg rH rH * 8 a 3 + 1 +1 +i Si roH >>» rH sj m CM c« CD 00 CO CM X! EC CO CO ^ rH m m CM CO
CD SH •P CD •P C! JA ~ «H J3 a CD 0 bO CD fl 0 & a •H c a >> •P a a M -H DO CO •H H rt iti •P •P
o rH +1 « 53 00 00 sz; CO r-4
O CM u 05 +1 +1 Jz; W m 00 t» CO CM T3 00 rt +> 00 m 03 00 CM OK CM H m 01 +1 +i + 1 * © w t> * * h t* CO CO
a> 0 DO C B •H 3 a 00 CO •rt >» +J m O +J •p «M A t>> u •rt r-4 (A •H iH 0) Q CD P 9 iH to OS DB +J M •H a a> •H o 0 01 05 +J n w -29-
In all cases where comparable data is available, the seasonal charges are the same, stomatal numbers were highest in leaf tissue formed during the drought of 1976 falling again in tissue produced during the wet autumn. It must be noted that these differences were not as marked as with the lowland populations. The changes and trends in the numbers of short- cells are less easy to interpret.
Experiment 5a Aim To test the plasticity of the above attributes under experimental conditions.
20 plants were collected at random from populations H, J, K, L. They were potted out in 20 cms. plastic pots, filled with John Innes No. 1 potting compost. The 80 pots were randomised in a latin square in the greenhouse where they were watered daily for a period of 4 weeks.
At the end of the experiment the plants were harvested and the following attributes were measured on leaf samples from each. 1) Number of stomata; 2) Number of cells, on the new leaf tissue at the base and on the old leaf tissue produced during the autumn prior to collection. The results are summarised in Table 10 in which the results of statistical comparisons are presented. -30-
TABLE 10
Stomata and cells (sample size 10)
Field Stomata Cells Field 1) Population H top (521) 497 - 29 373 ± 14 (355) *.* NS 2) H base 641 - 27 403 ± 8 (362)
3) " J top (576) 574 - 30 43£ i 65 (453) ** NS
4) " J base 770 - 38 511 ± 56 (358) 5) " K top (596) 518 - 16 360 ± 27 (361) #** * 6) K base 713 - 42 496 - 38 (364) 7) M L top (541) 400 ± 38 384 - 28 (445) NS NS 8) L base 478 - 35 366 - 36 (378)
Conclusions
In all cases the number of stomata per unit area of leaf produced in the greenhouse were greater than that produced in the field. The increases were significant in all cases except population L from the deep wet soil.
This is in marked contrast to the greenhouse experiments carried out on the lowland population which, in every case, showed a decrease of stomata in the wet treatment. The number of short- cells showed no significant pattern of change under the experimental conditions. -31-
Study 4 Transpiration Experiment 6 Aim To compare the rate of transpiration of plants collected from field populations A and B in Cassop Vale.
Methods One hundred plants collected at random from each population in the field were potted individually in 20 cms polystyrene cups filled with commercial vermiculite.
All plants were kept under the same conditions of light and temperature in the laboratory. Fifty of each batch being watered daily (wet treatment), the other 50 being watered every 7 days (dry treatment). The experiment was begun after 14 days of laboratory growth.
Ten plants from each treatment were watered until the vermiculite was fully saturated after which they were allowed to drain for 10 minutes before being sealed as shown in Fig. 4
Each transpirometer was then weighed to an accuracy of 0.005 gms and the leaf area of each plant was calculated after measure• ment of the length and maximum width of each leaf.
The plants were then placed in a line on the laboratory bench, at right angles to the incident sunlight.
For the first four days each transpirometer was reweighed every 8 hours and then every 24 hours for a further 13 days after which all plants were showing signs of stress. Each time a transpirometer was weighed it was randomly replaced in another position in the line. v/q saline.
Soil
Cup drainage. holes
' IG 4 -33-
At the end of the experiment the leaf area of each plant was again measured.
Results The results are summarized in Table 11 below, and in Figs. 5 and 6. TABLE 11
Experiment 7
gms/cra2/Day - standard error
Days Dry in Dry Dry in Wet Wet in Dry Wet in Wet 1 0.12 + .04 0.43 + .05 0.56 + 0.07 0.33 ± .03 2 0.31 + .03 0.32 + .03 0.48 + 0.04 0.46 + .06 3 0.32 + .05 0.16 + .01 0.97 + .06 0.55 + .01 4 0.11 + .04 0.07 + .02 0.53 + .03 0.61 + .02 5 0.52 + 0.06 0.52 + .04 0.52 + .01 0.55 + .02 6 0.34 + 0.04 0.31 + .07 0.40 + .03 0.56 + .04 7 0.21 + 0.03 0.51 + .04 0.47 + .02 0.49 + .03 3 0.01 + 0.03 0.43 + .03 0.41 + .04 0.18 + .07 9 0.43 0.03 0.16 + .01 0.36 + .01 0.32 + .02 10 0.32 + 0.04 0.31 + .02 0.18 + .01 0.36 + .02 11 0.51 + 0.04 0.33 + .06 0.26 + .03 0.45 + .01. 12 0.26 * 0.02 0.36 + .03 0.22 + .02 0.28 + .04 13 0.13 + 0.01 0.14 + .01 0.17 + .01 0.21 + .02 14 0.10 + 0.03 0.21 + .01 0.18 + .06 0.22 + .03 15 0.12 + 0.02 0.09 + .02 0.09 + .03 0.19 + .07 16 0.07 + 0.01 0.13 + .01 0.16 + .01 0.19 + .01 17 0.09 + 0.01 0.26 + .07 0.23 + .06 0.46 + .02 18 0.06 + 0.01 0.20 + .03 0.29 + .04 0.28 + .04
MEANS 0.22 0.27 0.36 0.37 -34-
Table 11 (Cont'd)
Student t test
12 3 4 Dry in Dry 1 NS NS ** Dry in Wet 2 NS NS Wet in Dry 3 NS Wet in Wet 4
Conelusions
The rates of transpiration show a definite gradation being greater in the plants of treatment 4 (vet in the wet) and least in treatment 1 (dry in the dry).
12 3 4 0.22 0.27 0.36 0.37
Only when the results of treatment 1 and 4 are compared is there any significant difference
It was concluded from the results of experiments 2 and 3 above that the number of stomata formed per unit leaf area was very plastic responding quickly to change in environment conditions, It was therefore decided to carry out a further experiment.
Transpiration Experiment 7 Aim To compare the rate of transpiration of the two populations A and B from Cassop Vale after a longer period of growth under the experimental conditions in the greenhouse. -35-
In the light of the results of experiment one only the two extreme treatments were used, dry in the dry, and wet in the wet. The plants were grown under the experimental conditions in the greenhouse for 28 days prior to the beginning of the experiment.
The method employed were exactly the same as those used in experiment 1.
Results The results are summarised in Table 12.
TABLE 12
Days Dry Dry Wet Wet 1 0.63 + .03 0.52 - .06 2 0.44 + .03 0.43 - .06 3 0.38 + .07 0.91 - .05 4 0.42 + .06 0.26 ± .03 5 0.31 + .05 0.23 - .03 6 0.11 + .06 0.13 - .07 7 0.36 + .04 0.21 ± .03 8 0.27 + .05 0.14 - .05 9 0.13 + .03 0.08 - .06 10 0.34 + .06 0.32 ± .05 11 0.45 + .06 0.36 - .03 12 0.35 + .04 0.34 ± .05 13 0.42 + .07 0.51 - .06 14 0.41 + .03 0.32 ± .06
MEANS 0.358 0.340
T Test on Means
DD WW
DD NS WW I I i t ( I; t P::! hG. .0.....WATER".Los.s...OVER.isx;rwo DA* s .OF cxPERinENX
i i
t
• 2o i i 1 t:::.l
35
I. i. 00 : I t i r-:-:i 0 ! 1 I jL • t
i 'i ! 1 i .it .DRV-*WCT i i i ! i-:::t; i 1 - • • ( 1 1 f •A +. T .1 ISO. 1 ii i I 1 • 1
I f 1 I J I :t I3D;
•
> 2o! • :t: 0 1
DRV-»DRr t loo i
I I
1
.1 I t •I
li • 70 i t : ;1 1 f
I - t
r-1 - r.::-.l 1
t 1 n 1 I I 3o 1 J
i t i:
t i::: I f i n i .i t i
r 1 DAy.2. -37-
7t> DRY —» DRY WET ->WET
bo
lo \
20
IO i ;•• ; 1 I i
i ' ! ' .' : - 12. 16 l« L^ S ia I fa 19 ' _ * j _ I . J . • V :- | j I - • J — - WET DRY-- . DRY—>-WEX_; < i ! ;
50
3o
20
to
lb t<6 ifc 19 : _.. Time ihcreme.-.ts of four days . _L _ J L : . ' : ; i 1 ; ' I • ; j r ' 1 • • • he. 6 WATER LOSS 1+ DAY MEANS THROUGHOUT EXPERIMENT I -38-
Conclusions There is no significant difference between the rates of transpiration in the two treatments.
Overall conclusions It is impossible to come to any lirm conclusion on the basis of these few, crude experiments.
However the indications are that the plants of population A (under the conditions of experiment 6) can control water loss from their leaves more efficiently than those of population B.
The graphs lend weight to this conclusion indicating that even over the first two days of the experiment when it appears that the plants are "settling down". A pattern of difference in the rate of transpiration between the population and the treatments is set up and this pattern is more or less maintained throughout the experimental period.
The fact that these differences become obscured after 28 days of growth in the greenhouse are best explained by 1) the great plasticity in the number of stomata per unit leaf area shown above and 2) the supposition that the bulk of transpiration takes place via the youngest leaf tissue.
Supporting although circumstantial evidence for the latter is provided by the fact that the main visible effect of stress over the period of the experiment was the rapid death of the leaves from the tip backwards toward the meristem. -39-
GENERAL DISCUSSION AND FURTHER EXPERIMENTS
In order to attempt to understand the effects of the environment on the structure and anatomy of the leaf of Sesleria a model of the development of the leaf blade is presented below Dead Tip FIG. 7
Blade Blade meristem Leaf sheath X=2 Culm
Initiation of the structure of the epidermis including the frequency of the stomata and the short cell groups must take place in the leaf blade meristem, Thiele (1951).
Investigations were made into development in the region of the meristem, FeUlgen method, but all attempts at revealing the pattern of mitotic divisions failed. The actual process of initiation and early development of the stomata is thus a matter of pure conjecture.
From the experimental work described above and summarised in Table 13 it may be concluded that there is no correlation between the number of stomata and the number of short cell groups formed per unit area of epidermis. In the light of this together with the absence of any overall pattern of response of the number of short cells to environmental conditions either in the field or greenhouse it was decided to omit the short cells from further discussion. -40-
TABLE 13
Summary of Resultss of all counts Number of Stomata per unit area and number of short-cells per unit
area in the same Tissue
Stomata Short-Cells Stomata Short-Cells
837 351 505 241 796 88 503 258 770 511 497 373 725 300 495 234 713 496 485 91 677 194 482 225 669 372 478 366 660 543 466 255 649 315 645 279 454 302 643 361 450 216 642 302 437 296 641 403 640 284 417 336 614 410 403 375 614 277 400 384 604 250 596 364 576 358 574 438 549 445 548 401 541 378 532 395 532 338 521 362 518 360 513 517 507 306 -41-
STOMATA
All the field data indicates that the number of stomata produced per unit area of epidermis is in some way related to a "scaler" linking depth and dampness of soil and water supply. The differences are most marked in the lowland populations, but nevertheless the trends throughout the montane populations are the same see summary table, 14.
TABLE 14
Soil Type Dry/Shallow Damp/Deep
Lowland Drought 837 715 640 604 505
Rains 725 NR NR NR 450
Montane Drought 677 660 643 549 NR
Rains NR 576 596 541
It is of interes5 t tO note that for each subjectively comparable step in the depth/dampness scaler the stomatal numbers are fewer in the montane populations. It must however be emphasised that the soil step units are in no way directly comparable.
Measurements of the soil moisture content (amount of water present in the air dried samples) of each soil type summarised in
Table 15, bear out the subjective assessment of depth and dampness.
TABLE 15
Soil Moisutre % (5 replicates)
Soil Type Dry/Shallow Damp/Deep
Lowland 3 - 0.7 10 - 3.6 15 - 6.0 23 * 7.3 34 + 1.6 Montane 5 - 2.2 8 - 4.1 12 - 1.7 20 - 11.2 36 - 14.1 -42-
It was impossible to collect relevant data on the microclimate of the two sites during the experimental work.
However data^ see Table 16 from the Upper Teesdale (Widdybank
Fell) and Durham Observatory Meterological stations do help to indicate the macro-differences between the climates of the two study areas throughout 1976.
The experimental work on plasticity back up the trends shown in the field populations at least as far as the lowland populations are concerned. The plants from the population A
(dry shallow soil) produced significantly fewer stomata when grown under the "wet" conditions. In marked contrast the plants of population B (deep damp soils) produced significantly more stomata when grown under "dry" experimental conditions.
These significant changes were found both on new leaf tissue and on new leaves produced during the experimental period.
As the depth of the potting compost was the same in each of the experimental treatments it must be concluded that water supply, hydrature of the soil/precipitation/evaporation system Walter(1973) is the main factor controlling the structure of the epidermis of Sesleria. The conditions of humidity in the greenhouse experiments were not kept stable although the fluctuations were similar for all plants in each experiment.
However it is realised that the humidity microclimate in and around the pots subject to more regular watering could be higher than that around those in the "dry" treatment.
i i The effect of hydrature on the stomatal number is also shown by comparison of the leaf tissue produced in the field during the summer drought and the autumnal rains of 1976. -43-
0) o CO O * • • • © rH rH Q mo o CoM
CO If) o CO > • • • • O CM cn CO CM cn
CO o M* 3 • * • • O CM CO I* JS o r-to CO bO rH CM 3 o O CM CM 00 CO .fl +> • • • • +J Pi CO CM oo cn © cn rH rH © CO rH CM fn © 3 fl +» rt cn iH 00 • • • U fl 00 co' CM rH iH CM rH &i < B (fl U -O fl fl 0 >» O CM IT) n -H iH • * * « "O 3 00 CO fl-ttwrt •"3 cro> iH CO rH cs "O -u fl (fl
H H H © cn 00 rH CM rt £ rt fl • • * • «H 0 O 3 CO 00 CO fl rH -H •-s CM rH CO rH •H bo «S -P 0 SH fl iH B$ 0 >» cn If) W > rH • • o • * fl © © S CO rH CO t- CS -H +J iH CO
fl CM 00 CM • • • • CD Q CM rH iH iH rH 1-1 5 A E 0 u o o «H B « a fl A •H a •H Ba ©s © 0«3 EH >> fn B O C8 +> fl X! CS ft > £ rH 3 U >»r-l Q © (0 •o © 43 •H O -44- In all cases the number of stomata produced during the rains were significantly fewer than the number produced during the drought. Turning to the montane populations the results of the experimental work, though at first sight puzzling are of great interest. In all cases except for the wettest field population, the number of stomata produced in greenhouse culture whether "wet or dry" were greater than the number produced in the field. This can only be explained by supposing that the conditions of both experimental treatments are more 'xeric' in terms of'hydrature'than those usually encountered by the montane populations in the field. Unfortunately it was impossible to make meaningful recordings of the humidity at the field sites during the growing period. The fact that all the 1976 field comparisons showed that the leaf tissue produced during the drought had significantly more stomata per unit area than that produced during the autumnal rains is good supporting evidence indicating similar behaviour of all the populations to an effective scale of hydra ture. PLASTICITY Perhaps the moot surprising results of the work outlined above is the rapid response in the number of stomata produced per unit leaf area in relation to hydrature both in the field and the laboratory. It would appear that as soon as the leaf blade meristem t i is put under a new regime of hydrature the rate of initiation of stomata changes, perhaps to compensate for the change , in water supply. -45- The importance of such plasticity to the success of a plant able to live across a range of habitats cannot be overstressed, cf. the findings of Clausen Keck & Hiesey for Achillea millefolium (1948). It is however obvious from the distribution of Sesleria that it is unable to compete with the ranker growing grasses of the Mesobromion proper Shimwell 1968, Bellamy e_t al. (1969). It has been suggested Lloyd (1974) that its inability to compete in the warmer conditions more typical of the Mesobromion may be due to its slow rate of growth compared with the more thermophilous grasses. TRANSPIRATION The experiments on transpiration rate although of a very 'crude' nature do give backing to the above conclusion. The rate of water loss being significantly less from the dry population A than from the 'wet' population B. West (1975) had attempted and failed to get meaningful estimates of transpiration in the field using a simple cobalt thiocyanate paper technique. His laboratory experiments using the same technique as employed in this study were less conclusive than those reported here. However the marked plasticity of the number of stomata reported here and the fact that Wests plants were grown in the greenhouse for one month prior to comparative study provides an adequate explanation for this. More accurate measurements on a range of contrasting populations would be necessary before valid conclusions could be drawn. However it does appear safe to suggest that an increased number of stomata per unit area of epidermis afford -46- better control of transpiration. The mechanism of such control has long been understood from the investigations of Browne & Escombe (1905), Kramer (1969). The tentative indications are that Sesleria plants collected from populations from a range of environmental conditions in which it grows in N.E. England respond to water stress by increasing the number of stomata per unit area of leaf tissue which help to control water loss from the plant. The two exceptions to this rule, populations H & M are of interest. Population H although growing on very shallow rapidly drying soils has significantly fewer stomata per unit area of epidermis than any of the other montane populations. An explanation is sought in the fact that the soils of population H are rich in heavy metals. A definite effect of the heavy metals on the biogeochemistry of the leaf tissue is shown by the following investigation. HEAVY METALS IN POPULATION H In order to investigate further the effects of heavy metals (if any) on Sesleria the following analyses were undertaken. Leaves were collected from the two populations, H (on heavy metal spoil) and J an adjacent dry shallow soils free from the effects of mining spoil. On return to the laboratory the dead tips were removed from all leaves the dead material being discarded. Six replicate samples of live leaf material were selected at random from each of the two population samples. After drying to constant -47- weight at 105°C they were wet digested with a mixture of perchloric and nitric acids using the method of Johnson & Ulricht (1959). The digests were analysed using a Perkin Elmer 480 atomic absorption spectrophotometer for Mg, Ca, Pb, Zn, Al & K. All results corrected for matrix enhancement Waughman (pers. comm.) are summarized in Table TABLE 17 mg per gm dry weight of plant tissue means + standard errors K Mg Cu Pb Zn Al HJ .H J HJ H JH J HJ 0.559 0.565 5.15 5.14 0.200 0.141 0.205 0.144 0.181 0.134 10.55 10.14 ±0.01 ±0.012 ±0.169 -0.233 ±0.017 ±0.021 ±6.010 0.008 ±0.019 ±0.012 ±0.152 ±0.233 Results of student t test, comparing element concentrations in leaf tissue of population H & J. Mg NS Ca NS Pb * Zn ** Al * K NS The levels of Pb, Zn and Al all of which are present in larger than'normal' amounts in the soils associated with heavy metal spoil heaps in Upper Teesdale Kookorinis (1976) are present in significantly greater concentrations in the tissues of population H than in the tissues of population J. The mechanism if any linking the significantly higher levels of heavy metals and the reduced number of stomata is obscure. Indeed it might be expected that high levels of such metals could result in physiological drought Raman (1911) -48- which might be expected to result in an increase in the number of stomata rather than a decrease. The results from population M are more readily explained. In this case although the soil was without doubt the 'wettest' studied being along the edge of a flush dominated by vegetation referable to the Eriophoretum latifoliae, it had significantly more stomata per unit area of epidermis than all the populations from 'drier' situations. Despite the fact all the plants were very small and stunted and their rooting depth was limited to less than 3 cm due to marked gleying of the flush soils. West (1975) reported some measurements of the root/shoot ratio of the plants he studied. Attempts were made to gain similar information for the plants used in this study. However, because of the length of time required to excavate the roots and the inaccuracies inherent in such work due to breakage of the finer roots it was abandoned early in the study. The experimental work in which changes in the number of stomata were obtained in similar depth of soil and over a time scale in which it was found that in all cases only limited growth of new roots had occurred are of interest. They indicate that the amount of roots present on a plant is not the most important factor controlling stomata1 number. Further studies on populations found growing in other extreme conditions ar>s required before any conclusions can be drawn. -49- MECHANISM OF MORPHOGENETICAL CHANGE West (1975) showed for the population he studied that there was a significant difference between the size of the Sesleria plants and soil depth at any one altitude. This is in the main borne out by this study, for in the majority of cases the plants growing on the dry shallow soil were smaller than those growing on the adjacent damp/deeper soils. In the light of these observations it would appear possible that the mechanism of change in the number of stomata per unit leaf area could be brought about by a simple reduction in the growth rate of the leaf, providing that the rate of production of stomata was a fixed attribute of the leaf meristem system. In order to gain information concerning this relationship the following investigations were carried out. METHODS The longest leaf of the twenty plants selected at random from the field populations A, B, C, G, H, J, K and L were collected and the following measurements made on each (1) Length of the longest leaf (2) Length of five stomata (see Fig. (3) Longitudinal distance between adjacent stomata in one cell line. All the above measurements were made on tissues produced during the drought of 1976. In addition the same measurements were made on the contrasting leaf tissue of population H, J, K & L produced during the autumnal rains of 1976. A final set of measurements were also made on the tissues produced in experiment 4 described above. -50- 00 • m /-N CO 00 m CD o rH Q O CD O o © s en O ^ O O m + 1 8> m p • O o• & • m >-H • m o +i d +i O +1 CO O +i rH CM 00 m rH s CM o 00 O •H 03 co (O o CO 00 o 00 o +1 CO Tt< O CO § •O -H 3> O • 01 o O o• 0) O co • m • o • co o +1 ^ O +i O +i * § s a 6 +i CN CO rH 00 • rH r5 CO l> rH >> ^-s Q0 o co O CO O +1 IS rH h O CO O CO O O co rt Q O • O • m • • • CD ^ O +i CO s CO O +l O +l CO • co CO rH 22 ^ CO O E CM iH CO O rH CM •H >, CM CD OS CM 00 S5 g + 1 CO £! Q q o CO O +1 m d +i m" J3 .a bo to m 0) a) a bo o c a a o at> -H >» o o u OS -H o o 0. •H H Q EH h A A -P as Q ca S o ca •H iH o 3 CO a o O o e a a (8 a a> © +» d x: -u U +» « © o « CO •u £ eg S bo g 5 09 -P -r-5 O c o TABLE 19 SUMMARY No. of Stomata Distance Length per unit area mm mm 837 0.090 0.040 660 0.074 0.036 643 0.062 0.048 642 0.095 0.026 614 0.100 0.033 596 0.084 0.038 576 0.068 0.036 549 0.092 0.046 541 0.100 0.054 521 0.096 0.042 505 0.060 0.030 454 0.100 0.033 -52 o CO o o 8 * o o o +1 +1 +1 00 IS CO CO o o o CO § O o O • o • o o o + 1 +1 +1 00 00 o o o o US o o o o d +1 +1 +i 00 CM 00 o o o in O o 8 o o o 6 +1 H-i +i oo CM CM o O o G O o •rl •P 03 ca ft 0) ft O O 3 EH o Q. o OH £1 O fl rt •P •P H « -P bo RESULTS The results are summarized in Tables 18, 19 and 20. DISCUSSION Inspection of the data shows that there is no simple relationship between the number of stomata per unit area and either of the cell measurements. It is therefore obvious that the adjustment in the number of stomata both in the field and in the laboratory are not brought about by a simple increase in the number of stomata produced in each cell line. The greenhouse experiment further shows that the longitudinal distance between the stomata does not change significantly although the actual length of the stomata would appear to be more plastic. Fig 8 a and b shows tracings of representative sections of the epidermis of the two contrasting populations A & B. In both the intercostal cell lines with stomata are in ranks of 3 sometimes 2 or 1. However in population A these are separated in the main by 3 lines of costal cells while in population B the number is usually 6. It would thus appear that adjustment in the number of stomata present per unit area of epidermis is brought about by an adjustment in the proportion of costal to intercostal cell lines. Unfortunately time did not allow further measurements to be made. -54- MftlN DISCUSSION CONTINUED The above findings are also of importance in relation to stomata1 control of transpiration. Parlange & Waggner (1970) state that interstomatal interference is likely to take place when interstomatal spacing is less than 3 times stomata 1 length. Lloyd (1974) obtained values of less than 3 for some British populations of Sesleria and suggested that this factor might contribute to their high stomata1 resistance and low rates of trans• piration and photosynthesis. In West's (1975) investigation he only found a value of less than 3 from one population on shallow soil from a lowland habitat. Unfortunately because of the marked grouping of the stomata, the measurements recorded above are of no use in calculating a meaningful figure for the ratios distance between stomata to length of stomatal pore. It is nevertheless obvious that in all cases the individual stomata within the stomatal groups are close enough to invoke some effects of interference. It is also clear that in the case of population A even the stomata of adjacent groups could lie within the sphere of each others influence. CONCLUSIONS The work detailed above indicates that for the plants of the populations studied:- (1) The number of stomata produced per unit area of the adaxial epidermis of ttie leaf of Sesleria is related to -55- the 'hydrature' sensu Walter (1973) of the system in which the plants are growing (2) That the less readily available water is to the leaf blade meristem the greater the number of stomata are formed per unit area of epidermis. (3) That the morphogenetic response to 'hydrature1 is very rapid and hence the morphology of the epidermis as regards to stomatal number is very plastic. (4) That the increased number of stomata is produced by a decrease in the number of files of intercostal cells. (5) That the increased number of stomata helps to control the rate of water loss from the leaf. (6) That part of this control may be due to interstomatal interference. (7) That much more work is required before any of the above conclusions may be regarded as anything more than mere indications. (8) That a fruitful line of research would be studies of both the anatomy and transpiration of cloned material grown under a variety of controlled conditions in a growth cabinet. 56 a- O' I mm X oPUL Tracing ,ole Tracing of photograph of acetate peel of epidermis REFERENCES BELLAMY D. J., BRIDGEWATER P., MARSHALL C. & TICKLE W. M. (1969) Status of the Teesdale Rarities. Nature, Vol. 222, No. 5190 pp. 238-243. BROWNE H. & ESCOMBE F. (1905) Stomatal control of transpiration. Proc. Roy. Soc. B, 76, 29. BRYAN (1967) Climosequences of soil development in the Peak District of Derbyshire. E. Midi. Geoq. 4, 251-261. BRAUN BLANQUET (1951) Pflanzensoziologie Grundzflge der Vegetationskunde Berlin 631 pp. CLAPHAM R., TUTIN T. & WARBURG H. (1957) Flora of the British Isles. Cambridge Univ. Press pp. 1586. CLAUSEN J., KECK D. & HESEY W. M. (1948) Experimental studies on the nature of species. III. Environmental responses of climatic races of Achilled. Carnegie Inst. Wash. Pub. No. 581, 129 pp. KRAMER P. J. (1969) "Plant and soil water relationships: a modern synthesis". McGraw-Hill Book Company pp. 350. K00K0RINIS E. (1976) An experimental study of the factors limiting plant growth in Upper Teesdale. M.Sc. Thesis, University of Durham. LLOYD N. D. H. (1974) "Comparative ecophysiological studies of some species from the flora of Teesdale". Ph.D thesis, University of Leeds. METCALFE C. R. (1960) Anatomy of the Monocotyledons I. Oxford University Press 731 pp. A -2- PARLANGE J. & WAGNER P. G. (1970) "Stomatal dimensions and resiestance to diffusion". PI. Physiol. 48: 337-342. PEARCY R. W. & WARD R. T. (1972) "Phenology and growth of Rocky Mountain populations of Peschampsia caespitosa at three elevations in Colorado". Ecology, 53: 1171-1178. PERRING F. H. & WALTERS S. M. (1962) "Atlas of the British Flora" Nelson & Sons, London. PEE LABY E. (1889) Etude anatomique de la Leville Graminees de la France. Ann. Sci. Nat. Bot. Ser. 8 8 227-246. PRAT H. (1932) L'Epiderme des Graminees. Etude anatomique et systematique. Ann. Sci. Nat. Bot., Ser. 10, 14, 117-324. RAMANN E. (1911) Bodenkunde Springer Berlin. 619 pp. WALTER H. (1973) Vegetation of the Earth in relation to climate and the ecophysiological conditions. Hiedelberg Sci. Lib. WALTER H. & LEITH H. (1967) Klimadiaqramm Weltatlas Jena. THEILKE (1951) Uber die Moglichkeiten der Perikinalchimarenbildung bei Grasern. Planta 39, 402-430. WEST I. M. (1975) An ecophysiological study of Sesleria cagrulea ssp. calcarea. M.Sc. Ecology Dissertation, University of Durham. 4 112 JAN 1978 J tar- BfBTion ,/ REFERENCES Phytosociological Nomenclature throughout is based on that advocated by - LOHMEYER w. et al. (1968) Contribution a L'unification du systeme phytosociologique. Pour L'Europe moyerme et nord- • occidentale. Melhoramento 15, 137-151. (All authorities quote in the syntaxonomic sections will be found in this paper.) SHIMWELL D. (1968) The Phytosociology of Calcareous grassland in the British Isles. Ph.D Thesis, University of Durham. For the naming of plant species the following references have be~n used. FLOWERING PLANTS DANDY J. E. (1968) List of British Vascular Plants. Br. Mus. Net. Hist. Lond. MOSSES WARBURG E. F. (1963) Census catalogue of British mosses. (3rd ed.) Brit. Bryol. Soc. Publ. Ipswich. LICHENS JAMES P. W. (1967) A new Check Lis.t of British Lichens. The Lichenologist, Vol. 3, 95^153. MY SPECIAL THANKS ARE DUE TO I. M. WEST FOR ALLOWING ME TO MAKE USE OF PLATES 1, 2 AND FIG. 4.